I. Field of the Invention
The present invention relates to compositions for fluid catalytic cracking processes.
II. Description of the Prior Art
In an FCC process, metals accumulate onto the catalyst, the catalyst becomes deactivated with time and in order to maintain FCC unit activity, a fraction of the unit inventory is withdrawn and fresh catalyst is added. The spent catalyst (withdrawn catalyst) contains a dynamic mixture of catalyst particles from very old/high metals, low activity to newer/low metals high activity.
Antimony has frequently been added to cracking catalyst to "passivate" the catalyst and reduce the production of hydrogen and other undesirable light gaseous products, e.g., in U.S. Pat. Nos. 4,459,366, 4,457,693, 3,711,422, and 4,334,979.
Magnetic separation has been taught by a number of U.S. patents such as U.S. Pat. Nos. 4,406,773, 5,147,527, 5,106,486, 5,171,424, and 5,230,869 to Hettinger et al., which teaches the removal of inactive catalyst and sorbents from mixtures of active and inactive particulates so that the active particulates can be recovered for reuse.
However, it has not been previously taught that the passivating advantage of antimony on conversion on catalyst and sorbents can be coupled with the enhanced magnetic susceptible of metals to obtain the advantages of passivation and selective recovery of more active particulate.